std::basic_filebuf<CharT,Traits>::swap
Min standard notice:
Swaps the state and the contents of *this and rhs.
# Declarations
void swap( std::basic_filebuf& rhs );
(since C++11)
# Parameters
rhs: another basic_filebuf
# Return value
(none)
# Notes
This function is called automatically when swapping std::fstream objects, it is rarely necessary to call it directly.
# Example
#include <fstream>
#include <iostream>
#include <string>
int main()
{
std::ifstream fin("test.in"); // read-only
std::ofstream fout("test.out"); // write-only
std::string s;
getline(fin, s);
std::cout << s << '\n'; // outputs the first line of test.in
fin.rdbuf()->swap(*fout.rdbuf()); //swap the underlying buffers
getline(fin, s); // fails: cannot read from a write-only filebuf
std::cout << s << '\n'; // prints empty line
}